A fleet of Chinese military vessels have embarked on a journey toward the Baltic Sea to participate in joint drills with Russia.

AFP quoting Chinese state media as saying on Monday that three ships, headed by the Changsha destroyer, steamed toward Russia’s coasts at the Baltic Sea to link up with Russian vessels for drills near St. Petersburg and Kaliningrad in late July.

The fleet would include Chinese marines and ship-borne helicopters, according to Xinhua news agency.

China and Russia have been holding military exercises dubbed “Joint Sea” since 2012. The two have taken turns in hosting the drills, which many say are meant to counter the United States’ expanding naval activities in waters surrounding them.

The war games will take place at a sensitive political time, as US President Donald Trump is scheduled to visit NATO ally Poland, a country on the Baltic Sea, on July 5-6 ahead of his participation in the G20 summit in Germany.

Russia has been irked by NATO’s growing inclination to expand eastward while the Western military alliance has also increased its buildup along Russia’s western borders after a conflict erupted in Ukraine three years ago. Trump’s way of handling NATO and his criticism of European partners about their financial contribution to the alliance have raised questions about the extent of US president’s commitment to future NATO missions. Many expect Trump to revise his position during the visit to Poland next month.

Xinhua said this year’s edition of the joint drills with Russia would “improve coordination between the two navies on joint defense operations at sea.”

It added that the main objective was “to consolidate and advance the Sino-Russian comprehensive strategic partnership of coordination, and deepen friendly and practical cooperation between the two militaries.”

Russia joined Chinese ships in previous year’s drills in the South China Sea, a disputed vital trade route where other countries of the region challenge China’s construction of artificial islands.